Method and apparatus for inspecting substrates
US6548821B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 14, 2000 |
| Grant date | Apr 15, 2003 |
| Priority date | — |
| Expiry date | Apr 14, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/88
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Substrate inspection apparatus in accordance with the invention comprises optics for reflecting a laser beam off of a substrate and a detector for detecting the reflected laser beam. If a defect is present at the point where the laser reflects off the substrate, the laser will be deflected at an angle. Circuitry coupled to the detector generates a first signal that provides a measure of the extent to which the laser beam is deflected. (This signal is a measure of the slope of the defect walls.) An integrator receives that signal, and generates a second signal that is the integral of the first signal. The second signal is a measure of the height of the defect. The first and second signals provide a measure of the types of defects present on the substrate, and are used to determine whether the substrate is acceptable or should be rejected. In accordance with a second embodiment of the invention, laser beams are reflected off both the top and bottom surfaces of the substrate and detected by detectors. Circuitry coupled to each detector generates a signal indicative of the extent to which each laser beam is deflected by defects. In this second embodiment, the integrator integrates the …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.